Penile Polygraphy: The Admissibility of Penile Plethysmography Results at Sentencing in Tennessee

State judges in Tennessee currently consider the results of penile plethysmograph (“PPG”) evaluations when sentencing convicted sex offenders. These highly intrusive physical tests purport to identify whether an offender’s arousal is considered “deviant” by measuring the change in penis size after viewing various stimuli. Because the results are usually buried in psychosexual evaluations that are part of general presentence assessments of recidivism risk, PPG evaluations suffer from a lack of standardization and little attention under the rules of evidence. Interestingly, PPG testing is similar to polygraphy in a number of ways, although studies have shown that PPG results are more reliable than polygraph tests in determining whether a subject was truthful in reporting. For that reason, and the heightened importance of alternative sentencing decisions that prevent recidivism among individuals who cannot control their deviant sexual arousal, PPG results should be considered by judges only in limited circumstances. This Note provides a new rule of evidence modeled after New Mexico’s polygraph-admissibility rule, which provides practical standards to avoid unreliable results, consent requirements to ensure voluntariness, and opportunities to retake poorly conducted evaluations if good cause is shown. The proposed rule strikes a balance between society’s interest in safeguarding citizens from potentially dangerous sex offenders and the offender’s interests in protections from unwarranted government intrusion.